1. Field of the Invention
The present invention pertains to the reading and storing of data on machine-readable labels and, more particularly, to a device and method for reading, converting, and programming data in multiple media, including radio frequency identification tags and barcode labels.
2. Description of the Related Art
Various methods and systems exist for encoding data in machine-readable form, including devices that produce barcodes and related optical devices for reading barcodes, as well as radio devices such as transponders and radio frequency identification devices (RFID) or tags. These devices store information regarding an associated object that is tagged or labeled to permit machines to read the data associated with the object.
Barcodes generally consist of strips of dark and light indicia containing data that is optically read, and as such they provide a link between production, manufacturing, sales, and distribution of materials and the information associated with these materials. Printed data can be easily and automatically read by means of reading devices or scanners.
A barcode symbol consists of a barcode formed of colored bars and spaces. Barcode symbology can take many forms, such as normal code 39 shown in FIG. 1, which is a variable length symbology that can encode up to forty-four characters; extended 3 of 9 code that is a general purpose code capable of storing any ASCII character, code 93, which was designed to complement code 39 but has the advantage of being smaller; interleaved 2 of 5 used in the distribution industry for carton labeling where every interleaved 2 of 5 characters actually encodes two digits, one in the bars and one in the white spaces; code 128 that can handle any ASCII character and has eleven modules that may be either black or white with each character using three bars and three spaces; Codabar that is a general purpose barcode used primarily for numeric data and character symbols; the Zip+4 barcode used by the post office for sorting letters that is made up of tall and short bars with even spacing between the bars; UPC-A and UPC-E code that uses numeric symbology in retail applications for medium to small packages; and PDF417 that is a high density two-dimensional barcode symbology capable of encoding the entire ASCII set, the PDF standing for “portable data file” because it can encode as many as 2,725 data characters.
Barcode hardware typically consists of devices for producing and printing barcodes on labels, packages, and objects, and devices for reading and decoding the information encoded in the barcode, referred to as readers. Readers commonly take the form of wands that are a contact device dragged across the barcode in order to read and decode it. These are the least expensive of the barcode readers, and typically have a look and feel of a pen or pencil. Another reader is a charged coupled device (CCD) that utilizes solid-state technology to provide contact and non-contact scanning capabilities. While this device has an increased range and larger barcode reading capability than wands, the limitation is that the CCD technology can only scan as wide as the scan head. Laser technology provides high speed and longer focal length reading capabilities, but at the expense of utilizing moving parts, such as a mirror system. Focal ranges vary from three inches to thirty inches in most laser-configured readers.
While barcodes are a relatively recent technology and remain in continuous evolution and increasing use, such as on moving objects, delivery notes, warehouse schedules, labels, it is essential that the barcode be legible and that visual access to the barcode be available to enable reading. Barcodes cannot be read through adverse environmental conditions, such as dirt, rain, and other impediments to optical access.
A more recent technology is remote communication utilizing wireless equipment that typically relies on radio frequency (RF) technology, which is employed in many industries. One application of RF technology is in locating, identifying, and tracking objects, such as animals, inventory, and vehicles.
RF identification (RFID) tag systems have been developed that facilitate monitoring of remote objects. As shown in FIG. 2, a basic RFID system 10 includes two components: an interrogator or reader 12, and a transponder (commonly called an RF tag) 14. The interrogator 12 and RF tag 14 include respective antennas 16, 18. In operation, the interrogator 12 transmits through its antenna 16 a radio frequency interrogation signal 20 to the antenna 18 of the RF tag 14. In response to receiving the interrogation signal 20, the RF tag 14 produces an amplitude-modulated response signal 22 that is modulated back to the interrogator 12 through the tag antenna 18 by a process known as backscatter.
The conventional RF tag 14 includes an amplitude modulator 24 with a switch 26, such as a MOS transistor, connected between the tag antenna 18 and ground. When the RF tag 14 is activated by the interrogation signal 20, a driver (not shown) creates a modulating on/off signal 27 based on an information code, typically an identification code, stored in a non-volatile memory (not shown) of the RF tag 14. The modulating signal 27 is applied to a control terminal of the switch 26, which causes the switch 26 to alternately open and close. When the switch 26 is open, the tag antenna 18 reflects a portion of the interrogation signal 20 back to the interrogator 12 as a portion 28 of the response signal 22. When the switch 26 is closed, the interrogation signal 20 travels through the switch 26 to ground, without being reflected, thereby creating a null portion 29 of the response signal 22. In other words, the interrogation signal 20 is amplitude-modulated to produce the response signal 22 by alternately reflecting and absorbing the interrogation signal 20 according to the modulating signal 27, which is characteristic of the stored information code. The RF tag 14 could also be modified so that the interrogation signal is reflected when the switch 26 is closed and absorbed when the switch 26 is open. Upon receiving the response signal 22, the interrogator 12 demodulates the response signal 22 to decode the information code represented by the response signal. The conventional RFID systems thus operate with an oscillator or clock in which the RF tag 14 modulates a RF carrier frequency to provide an indication to the interrogator 12 that the RF tag 14 is present.
The substantial advantage of RFID systems is the non-contact, non-line-of-sight capability of the technology. The interrogator 12 emits the interrogation signal 20 with a range from one inch to one hundred feet or more, depending upon its power output and the radio frequency used. Tags can be read through a variety of substances such as odor, fog, ice, paint, dirt, and other visually and environmentally challenging conditions where bar codes or other optically-read technologies would be useless. RF tags can also be read at remarkable speeds, in most cases responding in less than one hundred milliseconds.
A typical RF tag system 10 often contains a number of RF tags 14 and the interrogator 12. RF tags are divided into three main categories. These categories are beam-powered passive tags, battery-powered semi-passive tags, and active tags. Each operates in fundamentally different ways.
The beam-powered RF tag is often referred to as a passive device because it derives the energy needed for its operation from the interrogation signal beamed at it. The tag rectifies the field and changes the reflective characteristics of the tag itself, creating a change in reflectivity that is seen at the interrogator. A battery-powered semi-passive RF tag operates in a similar fashion, modulating its RF cross-section in order to reflect a delta to the interrogator to develop a communication link. Here, the battery is the source of the tag's operational power. Finally, in the active RF tag, a transmitter is used to create its own radio frequency energy powered by the battery.
The range of communication for such tags varies according to the transmission power of the interrogator 12 and the RF tag 14. Battery-powered tags operating at 2,450 MHz have traditionally been limited to less than ten meters in range. However, devices with sufficient power can reach up to 200 meters in range, depending on the frequency and environmental characteristics.